Many wells today have a deviated bore horizontally drilled extending away from a generally vertical axis main well bore. The use of horizontal drilling technology has increased production fourfold over that previously achieved from vertical wells. The drilling of such sidetracking is accomplished via multiple steps. After casing and cementing a well bore, historically a multi-stage milling process is employed to vertically mill cut a window through one side of the casing. Once a vertical window is milled through the casing at the desired sidetrack or kickoff location, a directional or horizontal well drilling process may begin.
Although simple in concept, the execution of casing window milling is complicated and difficult to achieve in a timely fashion. Several complicating factors are that the well bore casing is made of steel or similarly hard material and the casing is difficult to access down a deep well borehole.
A whip-stock wedge must be placed in the casing at the desired well bore depth location and locked in place in the direction for sidetracking, as disclosed in U.S. Pat. No. 5,109,924. The whip-stock wedge can then deflect the vertical rotating milling cutter's path to one side of the casing, for milling a sidetrack or kickoff window opening through that side of the casing. The sidetrack window entry point machined through the steel casing is narrow at the top, and can cause the sidetracking rotating drill pipe to be damaged and break, because of the rubbing of the rotating drill pipe against the narrow top window opening and burrs left on the machined casing. Historically it is not uncommon to take 10 hours to complete the milling of the window profile(s) through the casing using conventional machining processes.
Abrasive casing cutting with jet nozzles has been attempted to replace conventional milling, but the present abrasive cutting processes cannot achieve proper casing window cutting required for sidetracking or horizontal drilling.
A prior art method and apparatus for cutting round perforations and an elongated slot in well flow conductors was offered in U.S. Pat. No. 4,134,453, which is hereby incorporated by reference as if fully set forth herein. The disclosed apparatus has jet nozzles in a jet nozzle head for discharging a fluid to cut the perforations and slots. A deficiency in this prior art method is that the length of the cuts that the disclosed jet nozzle makes into the rock formation is limited because the jet nozzle is stationary with respect to the jet nozzle head.
Another prior art method and apparatus for cutting panel shaped openings is disclosed in U.S. Pat. No. 4,479,541, which is hereby incorporated by reference as if fully set forth herein. The disclosed apparatus is a perforator having two expandable arms. Each arm having an end with a perforating jet disposed at its distal end with a cutting jet emitting a jet stream. The cutting function is disclosed as being accomplished by longitudinally oscillating, or reciprocating, the perforator. By a sequence of excursions up and down within a particular well segment, a deep slot is claimed to be formed.
The offered method is deficient in that only an upward motion along a well bore is possible due to the design of the expandable arms. Furthermore, the prior art reference does not provide guidance as how to overcome the problem of the two expandable arms being set against the well bore wall from preventing motion in a downward direction. A result of the prior art design deficiency is that sharp angles are formed between the well wall, thereby causing the jet streams emitted at the jets at the distal ends of the expandable arms to only cut small scratches into the well bore walls.
A further prior art method and apparatus for cutting slots in a well bore casing is disclosed in U.S. Pat. No. 5,445,220, which is hereby incorporated by reference as if fully set forth herein. In the disclosed apparatus a perforator is comprised of a telescopic and a double jet nozzle means for cutting slots. The perforator centered about the longitudinal axis of the well bore during the slot cutting operation.
The perforator employs a stabilizer means, which restricts the perforator, thus not allowing any rotational movement of the perforator, except to a vertical up and down motion. Additionally, the lifting means of the perforator was not shown or described.
An additional prior art method and apparatus for cutting casing and piles is disclosed in U.S. Pat. No. 5,381,631, which is hereby incorporated by reference as if fully set forth herein. The disclosed apparatus provides for a rotational movement in a substantially horizontal plane to produce a circumferential cut into the well bore casing. The apparatus drive mechanism is disposed down hole at the location near the cut target area. The prior art reference is deficient in that the apparatus requires multi-hoses to be connected from the surface to the apparatus for power and control.
The prior art methods are also deficient in that often the cutting line established by the cutting nozzle creates a pie or fanned shape cut as it penetrates the casing. This causes difficulty in removing the pieces cut out by conventional means, due to the fact the rear face of the piece is larger than the opening cutout by the cutting tool. This necessitates either additional cutting of the target or the angling of the line of cutting to compensate for this problem and thus yield a rear face of smaller dimensions than the front face of the casing.
Additionally, existing nozzles attempting to use a coherent abrasive laden fluid while under water (or within another liquid) have to displace the water with a gas for effective cutting of a target greater than 150 mm distance from the nozzle.
There is a need for an abrasive-jet-fluid cutting nozzle and system that is capable of creating any desired opening in the casing(s).
There is a need, therefore, for a method and apparatus of cutting precise shape and window profile(s), which can be accomplished more quickly and less expensively.
An additional need is to perforate casings, cut pilings below the ocean floor and to slot well bore casings using the unique programmed movement of a jetting-shoe.